Apparatus for backflushing a producing formation penetrated by a well



Jan 15 1963 J. K. BECKETT 3 APPARATUS FOR BACKFLUSHING A PRODUCING FORMATION PENETRATED BY A WELL Filed Nov. 25, 1959 IN VEN TOR. JOSEPH K. EEC/(677' United States Patent 07 APPARATUS FOR BACKFEUSHING A PRODUCING FORMATION PENETRATED BY A WELL Joseph K. Beckett, Yor'na Linda, Calif, assignor to Western Gulf Oil Company, Los Angeies, Calif, a corporation of Delaware Filed Nov. 25, 1959, Ser. No. 855,344 7 Claims. (Cl. 16668) This invention relates to the treatment of oil producing formations and more particularly to apparatus for backflushing a producing formation.

During production from a well, solid materials sometimes plug the flow passages into the well bore and severely reduce the rate of production from the well. Silt and sand may migrate in the formation and plug fissures within the formation or may pack around the perforated liners often set through weak and unconsolidated formations and plug the perforations in the liner. It then becomes necessary to dislodge the particles from their position plugging the flow passages into the well bore to allow satisfactory rates of production to be attained.

The usual procedure to correct plugging of the formation and liner with solid materials is to reverse the direction of flow in the well periodically or to backflush the producing formation with a relatively lange volume of a cleaning liquid. The resultant backfiow dislodges solid particles which are wedged in the flow passage and either reorients them to increase the size of the openings or allows the particles to flow into the well from which they can be removed with subsequent production from the well. One method of obtaining the desired reverse flow for cleaning is by downswabbing the well and thereby forcing liquid standing in the well back into the producing formation. Sometimes, the downswabbing is not effective and it becomes desirable to lbackilush the formation with a cleaning liquid supplied from the well head. The backflushing operation is generally more effective than the downswabbing because of the possibility of using a cleaning liquid having the characteristics particularly adapted to remove the cause of the plugging and the possibility of using large amounts of cleaning liquid.

This invention resides in apparatus for backflushing a producing formation of a well having casing set in the formation, tubing extending down through the casing and a rod retrievable pump in the tubing for lifting liquids from the well in which a backflushing liquid is stored in the annulus between the casing and tubing directly above the producing formation. Upon lifting the pump, ports in the tubing string are uncovered to allow flow from the lower end of the annulus directly into the lower end of the tubing string and then into the producing formation.

In the drawings:

FIGURE 1 is a diagrammatic view of a well equipped for performance of the method of this invention showing the casing and a packer in vertical section and the remainder of the apparatus in elevation.

FIGURE 2 is a vertical sectional view of the portion of the tubing string containing the apparatus for uncovering the ports to allow flow from the annulus between the tubing string and casing into the tubing string.

FIGURE 3 is a vertical sectional View similar to FIG- URE 2 of a second embodiment of apparatus for allowing flow from the annulus into the tubing string for backflushing the formation.

Referring to FIGURE 1, a well, indicated generally by reference numeral 10, has a casing 12 set therein to a total depth 14 in a producing formation 16. Casing 12 is provided at its lower end with a perforated liner 18 through which production from the formationrlfi en- 3,073,390 Patented Jan. 15, 1963 ters the borehole of the well. The casing 12 is set in the well and cemented in place in accordance with the customary procedures.

Extending downwardly through the casing 12 and into the liner 18 at the lower end of the casing is a tubing string indicated generally by reference numeral 20. Tubing string 20 extends down the well to a depth such that its lower end opens into liquid in the well. A packer 22 in the tubing string near its lower end is set against the casing and closes the lower end of annular space 24 between the casing 12 and tubing string 20. Packer 22 is preferably set just above the upper boundary of the producing formation 16.

The upper end of the casing 12 at the well head is closed by any conventional means illustrated in FIGURE 1 for simplicity as a flat plate 26. The tubing string 20 extends upwardly through plate 26 and in turn is closed at its upper end by a cap 28. A sucker rod 30 connected at its lower end to a rod retrievable pump, not shown in FIGURE 1, extends upwardly through tubing string 20 and cap 28 for connection at its upper end with suitable driving means. The upper end of the sucker rod 30 can be connected, for example, to a piston in a hydraulic pumping unit or other conventional apparatus for providing reciprocating motion to the rod to drive the pump. Illustrated in FIGURE 1 is a clamp 32 engaging the sucker rod 30. Extending upward from clamp 32 are cables 34 which are connected to the walking beam of a pumping unit, not shown in the drawings. A clamp 29 on the upper surface of cap 28 is adapted to engage the sucker rod 30 for lifting the rod-retrievable pump in the manner hereinafter described.

A production line 36 extends from the side of tubing string 20 directly below the cap 28 for delivery of production from the well to suitable storage means, not shown in FIGURE 1. In the apparatus shown in FIGURE 1, pro-. vision is made for backilushing the producing formation with liquids produced from the well. For this purpose a branch line 38 from the production line 36 extends into casing 12 for delivery of the backflushing liquid into the annulus 24 between casing 12 and tubing string 25}. Line 38 is provided with a valve 40 for control of flow to the annulus of the well. i

Connected in the tubing string 20 a short distance above the packer 22 and forming a part of the tubing string is a perforated nipple 48. As shown in FIGURES 1 and 2, the upper end of perforated nipple 48 is connected to a collar 50 which in turn is connected to the lower end of a spacer nipple 54. A pump shoe 56 connects the upper end of the spacer nipple 54 to the portion of the tubing string 20 above the spacer nipple. The length of spacer nipple 54 is such that a rod retrievable pump 58, shown with a standing valve 69, is suspended in the tubing string with a bushing 62 at the lower end of the pump 58 positioned above the perforated nipple 48. Pump 58 is illustrated as being held in the tubing string 20 by a conventional top lock arrangement consisting of a seating ring 64, the upper surface of which is engaged by a shoulder 66 at the upper end of the pump 58. Pump hold down springs 67 engage the lower surface of seating ring 64 and hold the shoulder 66 tightly against the seating ring 64 to provide a seal closing the annulus between the pump and tubing string. A conventional bottom lock pump hold down could be used in place of the top lock arrangement shown in the drawings, in which event the spacer nipple 54 would not be required, and the seal between the pump and tubing string would be at the lower end of the pump.

Referring to FIGURE 2, an adapter nut 68 is connected by screw threads to the lower end of the perforated nipple 48 and in turn is connected at its lower end to a liner jacket 70. A lower adapter nut 72 similar to adapter nut 68 is connected to the lower end of liner jacket 70 and in turn is connected to the lower part of the tubing string 20 on which the packer 22 is mounted. Tubing spacer nipple 54, perforated nipple 48, and liner jacket 70 form a part of the tubing string 20. Fitting within the liner jacket 70 and held in place by engagement with the ends of the adapter nuts 68 and 72 are sealing means 74. The sealing means 74 are conveniently a section of a plunger pump liner of the type conventionally used in oil well pumps.

A tubular stinger 76 is connected to the lower end of the pump shoe 62 and extends downwardly through the perforated nipple 48 and sealing means 74 within the liner jacket 70. The tubular stinger in effect is merely an extension of reduced diameter of the bushing 62 and is preferably a section of a plunger of a tubing liner type pump. Such plungers are accurately ground to fit slidably and closely within pump liners in a manner which prevents leakage between the pump liner and pump plunger. Any suitable sealing means, for example rings of packing material adapted to engage the outer surface of stinger 76 can be used in place of the pump liner 74 illustrated in FIGURE 2 to provide the necessary seal.

In the assembly and operation of the apparatus, tubing string 20 is run into the casing and the packer 22 set. Rod retrievable pump 58 is then positioned in the tubing string with the seating ring 64 seated on shoulder 66 and with tubular stinger 76 extending through the sealing means 74, in the manner illustrated in FIGURE 2. Suitable reciprocating driving means are connected to the upper end of the sucker rod 30 and production is delivered from the well by the pump 58. During the period that the well is producing, liquid for backflushing the formation is delivered through line 38 into the annulus 24 between the tubing string 20 and the casing 12. The annulus is filled to a depth such that the hydrostatic head of the liquid in the annular space 24 above the perforated nipple 48 is higher than the pressure on the producing formation.

When it is desired to bacloflush, the rod retrievable pump 58 is lifted by means of the sucker rod 30 until the tubular stringer 76 is out of engagement with the sealing means 74. This may be accomplished without a production hoist by lifting the load on the sucker rod 30 with the walking beam of the pump, clamping the sucker rod in the elevated position by means of clamp 29, resetting clamp 32 on the sucker rod 30, and repeating the process until the pump 58 has been lifted high enough to move the stinger 76 above the sealing means 74. The liquid in the annular space 24 then flows inwardly through the perforations in perforated nipple 48 and then downwardly through the central opening in the sealing means 74 and the lower portion of the tubing string 20 into the perforated liner 18. The backflushing liquid flows outwardly into the producing formation to dislodge particles blocking the liner and the formation. Usually the hydrostatic pressure of the backflushing liquid in the annulus will be adequate to cause the desired backflushing. If additional pressure is required a pump and source of fluid or a compressor may be provided at the well head to increase the pressure in the annulus. After backflushing for the desired length of time, the pump 58 is again lowered to place seating ring 64 in engagement with beveled surface 66 and the hold down springs 67 and place tubular stringer 76 in the sealing means 74. The pump is then operated to lift liquids and entrained dirt or solid materials washed into the well during the backflushing operation to the well head. While the well is producing normally backflushing liquid is delivered into the annular space 24 to prepare for the next back flushing operation.

In the apparatus illustrated in FIGURE 3, a pump liner and pump plunger arrangement is used to close the cylinder opening in the tubing string 20 both above and below the perforated nipple 43 during normal operation. Referring to FIGURE 3, a top seal adapter nut 78 conmeets the perforated nipple with a top jacket liner 80. Within the top jacket liner is a pump liner 82 which is held in place within the liner jacket 80 by an adapter nut 84 which connects the liner jacket 80 to the spacer nipple 54. The operation of the apparatus illustrated in FIGURE 3 is similar to that described for FIGURE 2. To cause the backfiushing, the pump 58 is lifted in the tubing string until the lower end of the stinger 76 is out of engagement with the sealing means 74 to open the internal passage in the sealing means to liquids entering the tubing string through perforated nipple 48.

In the apparatus and process of this invention, the backflushing liquid is stored immediately adjacent the forma' tion to be backflushed thereby minimizing the lost time normally required when backfiushing wells. Although the invention has been described for backflushing with well fluids it is also suitable for use in processes where it is desirable to backfiush with liquids other than the well fluid which can be stored in the annulus until backfiushing is required.

I claim:

1. Apparatus for backfiushing an oil well havingcasing extending down the well to a producing formation and perforations in the casing opposite the producing formation comprising a tubing string extending down the easing to the vicinity of the producing formation, a packer above the producing formation engaging the tubing string and casing to close the annulus therebetween a perforated nipple in the tubing string above the packer, said perforated nipple having openings in the wall thereof, a pump within the tubing string above the perforated nipple, said pump having a tubular stinger extending downwardly from its lower end and through the perforated nipple for carrying well fluids from the producing zone to the pump, first sealing means in the tubing string above the openings in the perforated nipple adapted to prevent flow between the tubing string and pump when the pump is in operating position, second sealing means in the tubing string below the openings in the perforated nipple adapted to engage the stinger and prevent flow downward between the tubing string and stinger, said pump and stinger being movable upwardly from their operating position to a position out of engagement with the first and second sealing means whereby back-flushing fluid in the annulus above the packer can flow through the perforated nipple and then downward through the tubing string to the producing formation.

2. Apparatus for backfiushing a producing formation of a well having casing set therein and tubing extending down the casing, said casing having an opening therein opposite the producing formation, comprising a packer above the level of the opening in the casing closing the annular space between the tubing and casing, a perforated nipple in, and forming a part of, the tubing string above the level of the packer, first tubular sealing means in the tubing string above the perforated tubing nipple, second tubular sealing means in the tubing string below the perforated tubing nipple, a rod retrievable pump mounted in the tubing string above the perforated tubing nipple, a tubular stinger extending downwardly from the lower end of the rod retrievable pump through the tubing string to a level below the second tubular sealing means for the delivery of well fluids from the casing to the rod retrievable pump, said tubular stinger slideably engaging the first tubular sealing means and second tubular sealing means when the pump is in operating position to prevent flow between the stinger and the first tubular sealing means and the second tubular sealing means, said rod retrievable pump being moveable upwardly in the tubing string whereby the stinger is lifted from engagement with at least the second tubular sealing means to permit flow from said annular space above the packer through the perforated tu ing nipple and tubing string to the casing below the packer.

3. Apparatus for backflushing a producing formation of a well having casing set therein and tubing extending down the casing, said casing having an opening therein communicating with the producing formation, comprising a packer engaging the tubing and easing above the opening in the casing to close the annular space between the tubing and easing, a perforated nipple in the tubing string above the level of the packer, a rod retrie'vable pump in the tubing string above the perforated nipple, a string of sucker rods extending down the tubing string from the well head to the pump for actuating the pump, said pump having a tubular stinger extending from its lower end downwardly through the perforated nipple to a level below the perforated nipple, first sealing means in the tubing string sealingly engaging the pump and tubing string above the openings in the perforated nipple adapted to prevent downward flow of liquids discharged from the pump through the tubing string and out the openings in the perforated nipple, second sealing means in the tubing string below the perforated nipple adapted to engage and seal between the stinger and the tubing string and prevent downward flow around the stinger, said rod retrievable pump being vertically movable upwardly in the tubing string from the operating position for lifting the stinger out of the second sealing means to permit flow from said annular space through the perforated nipple into the tubing string.

4. Apparatus for backflushing the producing formation of an oil well having casing set to the producing formation and a tubing string extending down through the casing for the delivery of well liquids, said casing having an opening therein adjacent the producing forfation to allow flow from the producing formation into the casing, comprising a packer closing the annular space between the casing and tubing string above the level of the producing formation, a perforated nipple in, and forming a part of, said tubing string above the packer, a seating ring extending inwardly from the wall of the tubing string above the perforated nipple, tubular sealing means in the tubing string below the perforated nipple, a rod retrievable pump within the tubing string above the perforated nipple, said retrievable pump having a shoulder extending therefrom engaging the seating ring when the pump is in operating position, and a tubular stinger extending from the lower end of the retrievable pump below the seating ring and adapted to engage the sealing means to prevent flow between the stinger and tubing string, said retrievable pump being movable vertically upwardly within the tubing string whereby the tubular stinger is moved out of engagement with the sealing means to permit flow from said annular space through the perforated nipple and thetubing string to the casing below the packer.

5. Apparatus for back flushing the producing formation of an oil well having casing set to the producing formation and a tubing string extending down through the casing for the delivery of well liquids, said casing having an opening therein opposite the producing formation to permit flow from the producing formation into the casing, comprising a packer above the opening in the casing closing the annular space between the casing and tubing string, a perforated nipple in, and forming a part of, said tubing string above the packer, a seating ring extending inwardly from the wall of the tubing string above the perforated nipple, sealing means sealingly engaging the tubing string and extending inwardly therefrom below the perforated nipple, a rod retrievable pump within the tubing string above the perforated nipple, a

shoulder on the rod retrievable pump adapted to seat on the seatin ring when the pump is in operating position, resilient means extending from the pump and engaging the lower surface of the seating ring to releasably hold the pump in operating position, a tubular stinger extending from the lower end of the rod retrievable pump downwardly through the perforated nipple to engage the sealing means and prevent flow from said annular space through the perforated nipple and downwardly through the tubing string, and means for raising the rod retrievable pump in the tubing string whereby the tubular stinger is moved out of engagement with the sealing means.

6. In an oil well having casing set therein to a producing formation, said casing having an opening therein opposite the producing formation, tubing string extending down through the casing for the delivery of fluids from the well to the well head, a packer in the tubing string above the level of. the opening in the casing closing the annular space between the tubing string and casing, and a rod retrievable pump in the tubing string above the level of the packer, the improvement comprising a perforated nipple in and forming -a part of the tubing string between the packer and the lower end of the rod retrievable pump, a tubular stinger extending downwardly from the lower end of the pump through the tubing string to a level below the perforated nipple, and tubular sealing means in the tubing string below the perforated nipple slidably engaging the tubular stinger to prevent flow from the perforated nipple into the tubing string below the tubular sealing means, said rod retrievable pump being upwardly movable whereby on lifting the rod retrievable pump the tubular stinger moves out of engagement with the sealing means to permit flow from said annular space through the perforated nipple and the tubing string to the casing below the packer.

7. In an oil Well having casing set therein to a producing formation, said casing having an opening therein opposite the producing formation, tubing string extending down through the casing for the delivery of fluids from the well to the well head, a packer in the tubing string above the level of the opening in the casing closing the annular space between the tubing string and casing, and a rod retrievable pump in the tubing string above the level of the packer, the improvement comprising a perforated nipple in and forming a part of the tubing string between the packer and lower end of the rod retrievable pump, a tubular stinger extending downwardly from the lower end of the pump through the tubing string to a level below the perforated nipple, tubular sealing means in the tubing string below the perforated nipple slidably engaging the tubular stinger to prevent flow from the perforated nipple into the tubing string below the tubular sealing means, said rod retrievable pump being upwardly movable whereby on lifting the rod retrievable pump the tubular stinger moves out of engagement with the sealing means to permit flow from said annular space through the perforated nipple and the tub-ing string into the casing below the packer, and means for filling said annular space with a liquid for backflushing the producing formation.

References Cited in the file of this patent UNITED STATES PATENTS 1,958,170 Penrod May 8, 1934 2,307,662 Baylor Jan. 5, 1943 2,749,992 Hill June 12, 1956 

1. APPARATUS FOR BACKFLUSHING AN OIL WELL HAVING CASING EXTENDING DOWN THE WELL TO A PRODUCING FORMATION AND PERFORATIONS IN THE CASING OPPOSITE THE PRODUCING FORMATION COMPRISING A TUBING STRING EXTENDING DOWN THE CASING TO THE VICINITY OF THE PRODUCING FORMATION, A PACKER ABOVE THE PRODUCING FORMATION ENGAGING THE TUBING STRING AND CASING TO CLOSE THE ANNULUS THEREBETWEEN A PERFORATED NIPPLE IN THE TUBING STRING ABOVE THE PACKER, SAID PERFORATED NIPPLE HAVING OPENINGS IN THE WALL THEREOF, A PUMP WITHIN THE TUBING STRING ABOVE THE PERFORATED NIPPLE, SAID PUMP HAVING A TUBULAR STINGER EXTENDING DOWNWARDLY FROM ITS LOWER END AND THROUGH THE PERFORATED NIPPLE FOR CARRYING WELL FLUIDS FROM THE PRODUCING ZONE TO THE PUMP, FIRST SEALING MEANS IN THE TUBING STRING ABOVE THE OPENINGS IN THE PERFORATED NIPPLE ADAPTED TO PREVENT FLOW BETWEEN THE TUBING STRING AND PUMP WHEN THE PUMP IS IN OPERATING POSITION, SECOND SEALING MEANS IN THE TUBING STRING BELOW THE OPENINGS IN THE PERFORATED NIPPLE ADAPTED TO ENGAGE THE STRINGER AND PREVENT FLOW DOWNWARD BETWEEN THE TUBING STRING AND STINGER, SAID PUMP AND STINGER BEING MOVABLE UPWARDLY FROM THEIR OPERATING POSITION TO A POSITION OUT OF ENGAGEMENT WITH THE FIRST AND SECOND SEALING MEANS WHEREBY BACKFLUSHING FLUID IN THE ANNULUS ABOVE THE PACKER CAN FLOW THROUGH THE PERFORATED NIPPLE AND THEN DOWNWARD THROUGH THE TUBING STRING TO THE PRODUCING FORMATION. 